Divide the following complex numbers. $ \dfrac{-20-4i}{-4i}$
Since we're dividing by a single term, we can simply divide each term in the numerator separately. $ \dfrac{-20-4i}{-4i} = \dfrac{-20}{-4i} - \dfrac{4i}{-4i}$ Factor out a $1/i$ $\dfrac{-20}{-4i} - \dfrac{4i}{-4i} = \dfrac 1i \left( \dfrac{-20}{-4} - \dfrac{4i}{-4} \right) = \dfrac 1i (5+i)$ After simplification, $1/i$ is equal to $-i$, so we have: $\dfrac 1i (5+i) = -i (5+i) = -5i - 1i^2 = 1-5i$